Air Bag: Description and Operation

Driver Air Bag
The driver air bag is mounted in the center of the steering wheel. The unit consists of:
- Inflator.
- Ignitor.
- Mounting plate and retainer ring.
- Bag assembly.
- Steering wheel trim cover.

NOTE: The driver air bag unit is not a serviceable item, and must be serviced as a complete assembly.

Inflator
The inflator is a lightweight aluminum housing which contains the materials that generate the gases required for air bag inflation.The chemicals which generate the gas are normally very stable. In order for the chemical reaction to be initiated, an ignitor is installed to the center of the inflator. The ignitor converts the electrical signal to thermal energy, causing the ignition of the inflator gas generant. This ignition reaction combusts the sodium azide/molybdenum disulphide gas generant in the inflator, producing nitrogen gas, which inflates the air bag.

WARNING: THE AIR BAG INFLATOR CONTAINS MATERIALS THAT ARE TOXIC PRIOR TO COMBUSTION. IF THE METAL CANISTER IS RUPTURED, DIRECT CONTACT WITH THE GENERANT MAY BE MADE, AND MAY BE ABSORBED THROUGH THE SKIN. IN THE EVENT OF EXPOSURE, SEEK FRESH AIR, CONTACT A DOCTOR, AND WASH THOROUGHLY. DO NOT USE NEAR HEAT, ELECTRIC SPARKS OR FLAME.

Ignitor
The ignitor is used to convert the electrical signal from the diagnostic module into heat energy to activate the inflator.

The ignitor requires a nominal 3.1 amps for 3 milliseconds to activate, however, it will operate on a much smaller current than this.





Both the ignitor lead and the clockspring lead have plugs into which shorting bars are installed. When the plug is disconnected, the shorting bar shorts the other two ignitor leads to each other to prevent accidental electrical connection and subsequent inflation of the air bag.


Air Bag
The air bag is constructed of neoprene coated nylon, is 710 mm (28 inches) in diameter and fills a volume of about 65 liters (2.3 cubic feet) in approximately 40 milliseconds.

Mounting Plate and Retainer Ring
The mounting plate and retainer ring attach and seal the base assembly to the inflator. The mounting bracket is also used to attach the trim cover and to mount the entire unit to the wheel by means of four nuts.

Steering Wheel Trim Cover
The cover encases the air bag assembly. When the air bag is activated, a tear seam moulded into the steering wheel trim cover separates to allow inflation of the bag assembly.